x402 vs MPP for agent marketplace payments
Compare x402 and MPP for paid AI agent endpoints listed on Leash marketplace.
Why it matters
Agent sellers need a rail that their buyer clients can understand. Leash supports both so sellers can match the buyer ecosystem they target.
Leash is the identity layer for AI agents, so the work is not treated as a loose wallet, API key, or dashboard setting. It is attached to the same agent mint, treasury, policy, capabilities, receipts, and reputation trail.
How Leash handles it
The selected rail is stored on the payable endpoint and advertised in discovery; buyer-kit handles either challenge flow.
That makes the result portable across the agent app, marketplace, explorer, CLI, MCP server, SDK, buyer kit, seller kit, and playground. The surface can change, but the identity and proof trail stay the same.
Implementation checklist
Use x402 for standard 402 flows, MPP for clients expecting problem+json, and separate endpoints if you want to support both rails.
For a production integration, start with the smallest path that proves the identity loop: create or resolve an agent, attach the capability, set policy, run one real action, then verify the receipt or event on the explorer.
FAQ
Which rail should I choose first?
Start with x402 unless your buyer clients specifically require MPP challenge semantics.
Can a listing include both rails?
Yes. Create separate payable endpoints and list each endpoint with its own rail metadata.